For example, Patent Document 1 discloses a conventional technology of a work machine capable of regenerating a return hydraulic fluid from a hydraulic actuator.
Patent Document 1 discloses a hydraulic fluid energy regeneration device for a work machine. The hydraulic fluid energy regeneration device includes a regeneration hydraulic motor, a hydraulic pump, and an electric motor. The regeneration hydraulic motor is driven by a return hydraulic fluid discharged by a hydraulic actuator. The hydraulic pump is mechanically coupled to the regeneration hydraulic motor. With this hydraulic fluid energy regeneration device, the hydraulic pump mechanically coupled to the regeneration hydraulic motor can be directly driven by recovered energy. This eliminates losses that result from temporary energy storage. This, as a result, makes it possible to reduce energy conversion losses, leading to efficient use of energy.